Note: Descriptions are shown in the official language in which they were submitted.
200Z4~4
5-17297/1+2/+/MA 1947
Solid Herbicidal Preparations
The present invention relates to Granular herbicidalcompo-
sitions of hydroxy benzonitriles (HBN's) namely Ioxyniland
Bromoxynil.
These two active ingredients are normally prepared as esters
for Emulsifiable Concentrates (EC's) and as alkali metal
salts for other liquid formulations. The liquidformula-
tions, especially EC's containing esters, are toxiconskin
contact.
The HBN salts are soluble in water and this facilitates
dispersion of the formulation in aqueous systems. However,
these HBN salts, when processed as a dry powder are extremely
irritating to eye, nose and throat. Bearing this in mind,
the products are difficult to handle and also have theun-
desirable property of being very difficult to dry andthere-
forecannot be formulated easily with other watersensitive
activeingredients.
The HBN's in their phenol form do not have the sameirritancy
or drying problems associated with their salt counterparts.
Unfortunately, they are insoluble in water andcannoteasily
be formulated as soluble powders or granules.
The present invention overcomes this problem by formulating
the phenolic form of the HBN's with an alkali metal salt
which, on addition to water, causes an in situ neutralisation
to occur, forming the soluble salts of the HBN's.
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Accordingly, the present invention provides a composition
comprising ioxynil and/or bromoxynil in their phenolic form,
together with an amount of an alkali metal salt of a weak
acidwhich is preferably that which is stoichiometrically
requiredto react with the ioxynil and/or bromoxynil phenol,
in orderto form a water-soluble salt thereof.
By weak acid is meant an organic or an inorganic acid with
dissociation contant Ka between 10-8 and 10-3.
Sodium and potassium ions are preferred as alkali metal
kations.
Suitable salts of weak acids are, for example, acetates,
carbonates, hydrogencarbonates, hydrogenphosphites, di-
hydrogenphosphates, hydrogenphosphates, nitrites, hydrogen-
sulphites and polycarboxylates such as malonates.
Preferred alkali metal salts of weak acids are sodium-
carbonate, potassiumcarbonate, sodium acetate, sodium
malonate and sodium hydrogenphosphite. A very particularly
preferred alkali metal salt of a weak acid is sodium
carbonate.
Simple phenolic formulations can be prepared which contain
sodium or potassium salts of weak acids. These active
ingredients when added to the spray tank will dissolve,
leaving solutions of spray liquor. The benefits of using
these types of solid formulations are:
The less irritant and less moisture sensitive HBN phenols can
be used in the preparation.
The formulations in their solid form are very simple in their
composition and can be prepared with or without the use of
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wetting or dispersing aids. The formulations can contain
water-soluble carriers or fillers.
Compositions according to the present invention also maycon-
tain minor amounts of anionic surfactants. Suitableanionic
surfactants are polymer- or copolymer-moleculescontaining
hydrophilic groups which are capable of forminganions, for
example, polymer- or copolymer-moleculescontaining carboxyl
groups, sulfuric acid ester groups, sulphonic acid groups or
phosphoric acid ester groups.Preferred polymer-molecules are
polyacrylates, alkali metal salts ofdiisobutylene maleicacid
copolymers, ligninsulphonates andcondensed alkyl arylsulpho-
nates. A particularly preferredanionic surfactant isthe
sodium salt of diisobutylene maleicacid copolymer.
Suitable groups of water-soluble carriers or fillers may be
organicandinorganic salts, ureas and sugars. Preferred
water-soluble carriers or fillers are ureas and inorganic
salts.Particularlypreferred water soluble carriers or
fillers are inorganicsalts, forexample sodium sulphate,
potassium sulphate, sodium chloride, potassium chloride,
sodium nitrate, potassium nitrate and calcium nitrate but in
particularsodium sulphate.
The fact that the active ingredients and in many cases the
formulation dissolves in the spray tank gives rise to a non
sedimenting spray liquor which can be successfully sprayed
over an extended period of time.
Because of the solubility of the formulations, fine grinding
of active ingredients is unnecessary.
Another method of exploiting these formulations is that they
can be granulated to reduce the level of dust which is
generally considered as an undesirable property.
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Granulation of these formulations can be effected using
techniques such as compaction, extrusion, agglomeration or
spray drying. Compaction granulation involves compressing
dry powder components to form solid sheets which aresub-
sequently broken down into granules, using a suitable
crusher. Extrusion granulation comprises pressing a paste or
wetted powderofthe formulation through a screen; the
material extruded isthendried and broken down to granules of
a convenient size.Agglomeration granulation comprises
spraying a liquid, whichis usually aqueous, into a fluidized
powder. The powder agglomerates, form larger particles which
are subsequentlydried.
Spray drying granulation involves preparing a solution or
suspensionof the formulation, and spraying the solution or
suspension down a hot column of air. The droplets arethereby
dried to form spherical granules. In the case ofspray
drying, reaction will occur between the HBN phenol andthe
salt of the weak acid during the preparation of thesolution
or slurry. Consequently, HBN salt will be formed, therefore,
during this granulation technique. Salt formationmay also
occur, to some extent, during extrusion oragglomeration
granulation procedures, when quantities ofaqueous medium are
added prior to, and during granulationrespectively. No
detrimental effect is observed on thequality of theformula-
tion.
Another aspect of the formulation of the present invention is
the fact that the HBN components can be mixed with other
soluble active ingredients such as soluble salts ofchloro-
phenoxyalkanoic acids i.e. Mecoprop or sulphonylurease.g.
Triasulfuron. In the case of Triasulfuron, which is apotent
herbicide, the solubility increases with increasing pH. It
is insoluble at pH 2.5 but has a solubility of 1.5 g/1 at
pH7. However, in view of the hydrolysis of Triasulfuron at
low pH-values, pH 5-6representsanoptimum.
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-- 5
The granules produced in these cases still have the same
property of being fully dispersible and soluble once stirred
into the spray liquor.
The following Examples further illustrate the present
invention.
Examples l to 3: Compositions comprising ioxynil and
bromoxynil in their phenol form as well as a salt of a weak
acid are formulated and have the compositions as set out in
Table I.
Table I
Component % w~w % w~w% w/w
Ioxynil as phenol 30 30 30
Bromoxynil as phenol 30 30 30
Sodium Carbonate 15 20 to 100%
Sodium Sulphate to 100 % to 100 %
Sodium salt of maleic
acid diisobutylen copolymer 0 - 2 0 - 2 0 - 2
The powdered components are homogenised and then granulated
by one of the previously mentioned techniques. The result is
water soluble granules that eventually dissolve in the spray
liquor.
Example 4: A formulation similar to that of Examples 1 to 3,
but containing Mecoprop in salt form, is made up and has the
composition set out in Table II.
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Table II
Component % w/w
Ioxynil as phenol 5.0
Bromoxynil as phenol 5.0
Mecoprop asTriethanolamine salt 46.5
Sodium salt of maleic acid diiso-
butylene copolymer 2.0
Sodium Carbonate 1.0
Sodium Sulphate to 100 %
The powdered components may be homogenised ln a suitable
blender then granulated by first compacting then sieving to a
desirable particle size.
Example 5: The formulation defined in Table III is made up:
Table III
Component % w/w
Triasulfuron 0.25
Ioxynil as phenol 5.0
Bromoxynil as phenol 5.0
Mecoprop as magnesium salt or
Triethanolamine salt 46.75
Sodium salt of maleic acid
diisobutylene copolymer 1.0
Sodium Carbonate 1.0
Sodium Sulphate to 100 %
The formulation is granulated using the technique described
in Example 4.
